Telephone system



G. SANDALLS. JR

TELEPHONE SYSTEM Filed Aug. 16, 1934 VINVENT-OR GSANDALLS JR ATTORNEYPatented May 26, 1936 PATENT OFFICE TELEPHONE SYSTEM George Sandalls,Jr., North Tarrytown, N. Y.,

assignor to American Telephone and Telegraph Company, a corporation ofNew York Application August 16,

12 Claims.

This invention relates to telephone systems and particularly to paystation service systems in which a calling subscriber must deposit acoin before he can converse with the called subscriber.

An object of this invention is to improve and simplify pay stationcircuits for post-payment service. Another object is to provide paystation circuits that function without any special equipment at thecentral office.

Heretofore systems have been provided in which a transmitter. has beendisabled during certain periods of the call in which rectifiers havebeen used as blocking means, one in series with the transmitter and theother in parallel with the transmitter.

In these systems when a calling subscriber removes his receiver from thehook, the transmitter current is such that it may pass through thetransmitter and the rectifier in series therewith. When the called partyanswers, the current reverses at the central oflice and the transmitteris thereby disabled as the current passes through the rectifier in shuntof the transmitter. When the called party answers the calling party canhear the answer of the called party. The calling party then deposits acoin to momentarily open a connection in shunt of a resistance in theline. This causes apparatus at the central office to reverse the currentand thus permit the current to pass through the transmitter andrectifier in series therewith.

A feature of the present invention is a circuit arrangement of this typefor pay station use in which rectifier means are employed to disable thetransmitter by the reversal of current prior to payment and to make thetransmitter operative upon payment without again reversing the current.This feature may be embodied in an arrangement where one rectifier isplaced in series with the transmitter and another is placed in shunt ofthe transmitter and the first rectifier. Normally, the direction ofcurrent may be such that it passes through the transmitter and therectifier in series therewith and when the called party answers thecurrent reverses. The transmitter is thereby disabled by the currentpassing through the shunting rectifier. The calling party, however, canhear the answer of the called party. When the calling party thendeposits a coin, the series rectifier is short circuited and the pathfor the shunting rectifier is opened so that without again reversing thecurrent, the transmitter is made operative and without any rectifiers inthe transmitter circuit. Thus, a talking path is provided for thecalling subscriber 1934, Serial No. 740,167 (Cl. 17.96.3)

without any second reversal of. the current or any apparatus at thecentral office for providing such reversal. The apparatus. at thecentral office for reversing the current a second time as heretoforerequired in the prior art is thereby eliminated by the present inventionand the transmitter circuit during talking is freed from allencumbrances such as the rectifier in series therewith, heretoforeremaining in this circuit during talking.

Another feature is an arrangement in the above mentioned circuit wherebywhen the transmitter is made operative upon payment the dial or pulsecontacts are eliminated from the established connection. For thispurpose the dial contacts are normally placed in series with bothrectifiers and the transmitter and when a coin is deposited the dial.contacts are short-circuited. This feature therefore guards the systemagainst attempts to release an established connection and then to seizeanother connection without depositing another coin by manipulation ofthe dial contacts.

This invention will be clearly understood by reference to theaccompanying drawing. The section to the right of the dotted line AAshows schematically in part a line finder LF- and other apparatus at astep-by-step dial office including a relay 25 arranged to control thereversal of current supplied to conductors 38 and 39 from a bridgedimpedance battery supply in connection with. coil 26. Also there isshown anabbreviated schematic representation of a connector C withcontacts 48 and 49. This apparatus is all well known in the art, andonly that part of it necessary to explain the operation of thisinvention is shown. The section to the left of said line AA illustratesa subscribers 'postpayment station arranged in accordance with thisinvention which includes a transmitter, receiver, induction coil,condenser, ringer, switchhoolc'and. dial. There are also illustrated tworectifiers, one of which, designated [3, is connected in series with thetransmitter l2, and the other, designated I 4-, in multiple with thetransmitter I2 and rectifier l3. These rectifiers are poled to passcurrent in the direction indicated by the arrows and to block current inthe opposite direction. A coin switch is also: shown. This operates whena coin is deposited and is arranged to be locked in its operatedposition under control of. a hook actuated by the switchhookaforementioned.

A detailed description of the operation of' the arrangement shown in thedrawing will now be given.

Assume that a subscriber at the post-payment station, hereinbeforementioned, desires to establish a connection with another subscribersstation, not shown, but connected to a dial oflice, the apparatus ofwhich is partly shownat the right of line AA. To this end the subscriberremoves the receiver 4 from the switchhook 3. This causes the linefinder LE to function and close contacts 2| and 22. Other details of theline finder are not shown, the parts omitted being indicated by thedotted lines 38 and 39.

A circuit may now be traced through the contacts of dial 31 from thegrounded positive pole of a battery connection established by the linefinder, not shown, line finder contact 22, over conductor 42, throughswitchhook contact 3, transmitter l2, rectifier I3, conductor 4|,springs l8 and II of dial 3|, over conductor 48, winding I of inductioncoil 36, through line finder contact 2|, to the negative pole of saidbattery. In the circuit above traced current flows in the direction ofthe arrow of rectifier l3, and consequently rectifier |3 permits currentto pass through itself and transmitter l2. In shunt with transmitter l2and rectifier I3 a circuit path may be traced through rectifier l4 andcoin switch springs l9 and I1.

Through this shunt path, however, no appreciable current can flow atthis time, since the direction of fiow opposes the direction of thearrow of rectifier l4. This high resistance path through rectifier I4 isonly indicidental at this time. However, its useful functioning will bedescribed later in another connection. It is sufficient for the presentthat the path through transmitter l2 be of low resistance, as evidencedby the passage of current therethrough as described above, so that otherapparatus, not shown, at the dial office may be caused to function andto extend a talking connection through connective apparatus in the dialoffice leading towards the line of the called subscriber, such apparatusconsisting of automatic switches and relays, which are not shown here,The subscriber on receiving the usual dial tone, now operates dial 31and dials the number of the called subscriber. This causes pulsingcontacts l8 and H to interrupt a circuit which was in part previouslytraced. This circuit was hereinbefore traced from a grounded positivepole of a battery connection to switchhook contact 6. From this pointthe pulsing circuit proceeds through switchhook contact 5 and off normalcontacts 8 and 9 (which are closed when the dial is moved from itsnormal position) through pulsing contacts I0 and H and thence overconductor 48 by the circuit previously traced to the negative pole ofsaid battery. To avoid clicks in the receiver 4 while dialing dialcontacts and 8 are opened while the dial is off normal, thereby openingthe circuit through winding 2 of induction coil 36 and the winding ofreceiver 4.

The interruptions in accordance with dial pulses of the pulsing circuitcorresponding to the digits of the called number eventually effect aconnection from battery 44, windings of coil 26, conductors 21 and 3|,contacts 28 and 32 of relay 25, conductors 38 and 39, contacts 2| and 22at the line finder, through the calling subscribers loop as hereinbeforetraced, and also a connection through condensers 23 and 24 andconductors 33 and 34 to the called subscribers line, not shown. When thereceiver at the called station is removed from the switchhook, a bridgenot shown, is connected across conductors 33 and 34, causing theoperation of relay 25, through a circuit which may be traced fromgrounded battery 45 through the upper winding of relay 25 to conductor34, thence through said bridge, over conductor 33 and through the lowerwinding of relay 25 to ground. Relay 25 in operating reverses thepolarity of the current connected to line finder contacts 2| and 22 frombattery 44 and a circuit may now be traced, in the direction of currentflow from the grounded positive pole of battery 44, through the lowerwinding of coil 26, through contacts 29 and 28 of relay 25, conductor38, line finder contact 2|, through winding of induction coil 38conductor 48, contacts H and H) of dial 31, over conductor 4| torectifier I3, which is poled so as to prevent the passage of currentthrough it and transmitter l2. However, from junction point 43, thecircuit may be continued through contacts H and 9 and rectifier M toswitchhook contact 6. Rectifier I4 is so poled that current is nowpassed through it, and accordingly it acts as a low resistance shunt onthe series path consisting of rectifier |3 and transmitter i2. Fromswitchhook contact 6 the circuit continues over conductor 42 throughline finder contacts 22, conductor 39, contacts 32 and 30 of relay 25and upper winding of coil 26 to negative pole of battery 44. From thecircuit just traced it is seen that the reversal of current due to theanswer of the called subscriber has caused the disabling of transmitterl2, since as explained hereinbefore current is now blocked by theopposing rectifier |3 from passing through 2 transmitter |2 while therectifier I4 is so connected as to act as a low resistance shunt on theseries path including rectifier |3 and transmitter I2. Although thetransmitter I2 is thus rendered inefiective receiver 4 is so connectedthat the subscriber at the post-payment station can hear the answer ofthe called subscriber over the line through the normal receiver circuitcomprising condenser 20, winding 2 of induction coil 33, receiver 4,normally closed dial contacts I and 8, switchhook contacts 5 and 6 andconductor 42.

It is now necessary for the calling subscriber, in order to put the linein a conversational condition, to deposit a coin 43, the weight of whichcauses springs I5, I! and I8 to make contact and spring I! to break itsnormal contact with spring IS. The effect of this is to make thetransmitter effective for conversation, as will now be seen. It wasexplained hereinbefore that when the called subscriber answered and thecurrent was reversed that the passage of current through transmitter |2was blocked by rectifier l3, and that the transmitter was furtherdisabled by a shunting path through rectifier I4, which freely passe-dthe shunting current under this condition. When springs l5 and Il makecontact it is seen that rectifier I3 is short-circuited over an obviouscircuit and that the shunt due to rectifier I4 is opened when springs I9and I1 break. Consequently, current can now pass through transmitter l2over a circuit path from conductors 48 and 41, through springs l8, l1and I5, transmitter l2, switchhook contact 6 to conductor 42, and thenceover the circuit previously traced. When the subscriber at the paystation talks, current in the primary winding of induction coil 36fluctuates in accordance with the sound waves impressed on the diaphragmof transmitter I2, inducing corresponding cur rents in secondary winding2, which are conducted to the line in the usual manner through condenser28, winding 2, receiver 4, dial contacts 1 and 8, and switchhookcontacts 5 and 6. When spring |5 was depressed by the deposit of coin 43it locked in its operated position under control of spring 'fB, whichmoved to the left when the receiver 4 was removed from the switchhook 3.

At. the end of the conversation receiver 4 is restored to switchhook 3,which causes contacts 5 and 6 to open and release the apparatus at thecentral ofiice, and also spring I6 to move to the right releasing spring!5. The motion of spring It also causes coin 43 to be removed fromspring l5, thereby restoring springs l5, ll, 48 and I9 to their normalposition. It Will be noted that when springs I5, I1, I 8 and I 9 arestill in their operated position before the coin 43 is removed byrestoring the receiver 4 to the switchhook 3, the apparatus at thecentral oflice cannot be released by moving the dial contacts oifnormal, since the dial contact springs it and H are disabled over ashunt path including conductor 41, springs l8 and 1, and conductor 4!.It is thus impossible to dial another number without first disposing ofthe deposited coin 43 by restoring the receiver 4 to the switchhook 3.

The preceding description is for a call requiring the deposit of a coin.A description will now be made for the case where the pay stationsubscriber wishes to call an ofiicial number, for which nocharge is tobe made. In this case the subscriber dials the desired number aspreviously described and when the called party answers there is noreversal of line current and the current passes through transmitter. 62over the circuit previously traced in connection with an outgoing callfor a subscriber, before said subscriber answered and reversed thecurrent. Consequently it is now unnecessary to deposit a coin toconverse with the called party.

A call incoming from the central oifice will now be described. When thecalling subscriber (whose station is not shown) dials the number of thepay station, connection is made to the called line over conductors 5B,53, 52 and 5| and contacts 48 and 49 of an automatic connector C, thedetails of which are well known in the art and consequently need not beshown here. The omitted portions are indicated by the dotted linesrepresenting conductors 5s, 53, 52 and 5:1. As soon as a connection isestablished ringing current is applied and a circuit may be traced fromone terminal of the source of ringing current (not shown) over conductor50 through contact 48, over conductor 53, through ringer 35, condenser20, over conductor 52, through contact 49 and over conductor 5| to theother ringing terminal (not shown). Ringer 35 sounds when the subscriberin answering removes receiver 4 from the switchhook a bridge is closed,which causes the ringing current to be disconnected. This bridge is thesame as that previously traced through the apparatus of the subscribersstation for an outgoing call, before the called station answered andreversed the current. After ringing has ceased, battery and ground (notshown) are connected to conductors 5t and 5| respectively. It is assumedthat the battery terminal is negative and the ground terminal positive.Current will now flow through contacts 48 and 49 of connector C and overconductors 53 and 52 through a circuit at the sub scribers station,including transmitter l2 that was previously traced for a call outgoingfrom the pay station before current was reversed by the answer of thecalled subscriber. The station is now ready for conversation throughcontacts 48 and 49 of connector C and over conductors 5i] and 5|. At theend of the conversation, the

called subscriber replaces receiver 4 on the switchhook 3, and when thecalling subscriber also disconnects the connection is broken down atcontacts 48 and 49 of connector C, restoring all apparatus to normal.

What is claimed is:

1. A telephone set comprising a microphone, a circuit therefor,rectifier means in said circuit for short-circuiting said microphoneduring a certain period of a call from said set, and means for entirelyeliminating said rectifier means from said circuit during other periodsof said call.

2. A telephone set comprising a microphone, a circuit for saidmicrophone, rectifiers in said circuit effective on current reversal insaid circuit while making a call from said set for short-circuiting saidmicrophone, and means thereafter operative for entirely excluding saidrectifiers from said circuit to permit said reversed current to passthrough the microphone.

3. A telephone set comprising a microphone, a circuit therefor, arectifier in said circuit in series with said microphone, a rectifier insaid circuit in parallel with said microphone and said first mentionedrectifier, and means operative upon payment for shunting the rectifierin series with the microphone and for opening the connection in saidcircuit for the rectifier in parallel with the microphone.

4. A telephone set comprising a microphone and a dial, a circuit forsaid microphone and dial, rectifier means in said circuit forshort-circuiting said microphone during a certain period of making acall from said set, and means for eliminating said rectifier means fromsaid circuit and shortcircuiting said dial during other periods of saidcall.

5. A telephone set comprising a microphone and a dial, a circuittherefor, rectifiers in said circuit efiective on current reversal insaid circuit while making a call from said set for shortcircuiting saidmicrophone, and means thereafter operative for entirely excluding saidrectifiers from said circuit to permit said reversed current to passthrough the microphone.

6. A telephone set comprising a microphone and dial contacts, a circuitfor said microphone and dial contacts, rectifier means in said circuitfor preventing the passage of current through said microphone during acall from said set, and means for entirely eliminating said rectifiermeans from said circuit to allow passage of currents through saidmicrophone during certain other periods of said call.

7 A telephone pay station comprising a microphone and dial contacts, acircuit for said microphone and dial contacts, rectifier means in saidcircuit for blocking of speech current of one direction through themicrophone prior to payment and means for eliminating said rectifiermeans and dial contacts from said circuit upon payment to permit thepassage of speech current of said direction through the microphone.

8. A telephone pay station comprising a microphone, dial contacts,rectifiers, a circuit including one of said rectifiers in series withsaid microphone and another of said rectifiers in shunt of saidmicrophone and said first mentioned rectifier and said dial contacts inseries with said rectifiers and microphone, said first mentionedrectifier blocking current of one direction through said microphone andsaid second mentioned rectifier passing current of said one direction inshunt of the microphone, and means responsive upon payment foreliminating said rectifiers and said dial certain period of a contactsfrom said circuit to sage of current of said one the microphone.

9. A telephone pay station comprising a microphone, dial contacts, tworectifiers, a circuit for connecting one rectifier in series and theother in parallel with said microphone and both rectifiers in serieswith said dial contacts, means operative prior to payment for preventingcurrent from passing through said microphone by the aid of saidrectifiers, and means operative upon payment for permitting the passageof current through said microphone without passing through saidrectifiers and said dial contacts.

10. A telephone pay station comprising a circuit, a microphone in saidcircuit, a rectifier in said circuit in series with said microphone, arectifier in said circuit in parallel with said microphone and saidfirst mentioned rectifier, dial contacts in series with one of saidrectifiers, and means operative upon payment for shunting the rectifierin series with the microphone for opening said circuit for the rectifierin parallel with the microphone and for shunting the dial contacts.

11. In a telephone pay station, a microphone, two rectifiers, pulsingand off-normal dial contacts, switchhook contacts, coin operatedcontacts, a circuit arrangement for establishing a talking connectioneffective on the operation of the switchhook contacts, a circuitarrangement for establishing a dialing connection effective on theoperation of the off -normal contacts, a circuit arrangement effectiveon the reversal of current to the pay station for preventing a currentpassing through the microphone, said circuit arrangement including onerectifier blocking the passage of said current through the microphoneand the permit free pasdirection through other rectifier by-passing saidcurrent past the microphone and a circuit arrangement effective on theoperation of the coin operated contacts for establishing a talkingconnection through the microphone without again reversing the current.

12. In a telephone pay station, a microphone, two rectifiers, pulsingand ofi-normal dial contacts, switchhook contacts, coin operatedcontacts, a circuit arrangement for establishing a talking connectioneffective on the operation of the switchhook contacts including thepulsing contacts, a first rectifier, the microphone and the switchhookcontact in series, a circuit arrangement for establishing a dialingconnection effective on the operation of the off-normal contacts, saidconnection including the dialing contacts, the ofi-normal contacts andthe switchhook contacts in series, a circuit arrangement effective onthe reversal of current to the pay station, for blocking the passage ofsaid current through the microphone, including the pulsing contacts,certain of the coin operated contacts, the second rectifier and theswitchhook contacts in series with said second rectifier in the currentpassing direction and the microphone and the first rectifier in serieswith said first rectifier in the current blocking direction, and acircuit arrangement effective on the operation of the coin operatedcontacts for establishing a talking connection through the microphonewithout again reversing the current, including the opening of theconnection for the second rectifier and shortcircuiting the pulsingcontacts and the first rectifier and the closing of a connection throughthe microphone through certain of the coin operated contacts and theswitchhook contacts only.

GEORGE SANDALLS, JR.

DISCLAIMER 2,041,964.Ge0rge Sandalls, J12, North Tarrytown, N. Y.TELEPHONE SYSTEM. Patent dated May 26, 1986. Disclaimer filed May 29,1937, by the assignee,

American Telephone and Telegraph Company. I Hereby enters thisdisclaimer to claims 3 and 11 of the above numbered patent.

[Ofiic'ial Gazette, June 22, 1937.]

